During manufacture of semiconductor devices such as semiconductor memory devices, often a plurality of trenches are formed in the surface of a semiconductor substrate using, for example, reactive ion etching (RIE) or other known processes. The trenches are then filled with a silicon material. The silicon deposits in each trench form, for example, capacitors in a semiconductor memory device.
The filling of the trenches with silicon material must be performed so as to reduce, and ideally eliminate, voids and seams (gaps and other undesired openings) in the deep trench filling material.
According to known processing methods, silicon films are formed inside each deep trench using, for example, low pressure chemical vapor deposition. When the wafers are removed from the deposition furnaces, unintentional oxide films (e.g., native oxide films) are formed on the deposited silicon films due to exposure to the ambient atmosphere. Thus, subsequent annealing (to actuate dopants in the deposited silicon films, for example) is performed with unintentional oxide films on the silicon films. As a result, the known process results in numerous voids and seams in the trench filling material.
These voids and seams result in preferential etching during recess etching of the trench filling material during subsequent manufacturing steps. Furthermore, such voids and seams cause dislocations in the silicon substrate during oxidation processes performed after recess etching steps. Preferential etching and/or dislocation may result in such flaws as contact isolation or increases in node resistance. As a result, seams and voids formed in the trench filling material result in a lesser quality of performance of the semiconductor device.
Thus, there is a need for a deep trench filling method by which such voids and seams in the trench filling materials are greatly reduced or eliminated.